Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.1.1.67 (thiopurine methyltransferase)
 551 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Drug-metabolizing enzymes are responsible for the activation or detoxification of cytotoxic drugs. Allelic variants are present with a variable frequency in different populations around the world and have an important role in the therapeutic index of such drugs. It is known that polymorphisms in thiopurine methyltransferase and dihydropyrimidine dehydrogenase have been associated with altered drug metabolism and increased risk of severe toxicity from 6-mercaptopurine and 5-fluorouracil, respectively. Additionally, a variant number of dinucleotide-repeat sequences in the promotor for uridine 5'-diphosphate glucuronosyltransferase 1A1 influences the glucuronidation of SN-38, the active metabolite of irinotecan, which is associated with severe toxicity, including diarrhea and neutropenia. In the same way, polymorphisms in thymidylate synthase have been associated with pyrimidine-associated toxicity and also with response to chemotherapy. The examples shown in this review demonstrate the usefulness of pre-screening patients for well-characterized polymorphism to identify the best-tolerated and most-effective treatment.
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PMID:Genetic determinants of cancer drug efficacy and toxicity: practical considerations and perspectives. 1616 69

In recent years, pharmacogenomics have received much attention from the increased expectations for so-called order-made medicine. It is experientially clear that inter-individual differences exist in the degree of efficacy and occurrence of adverse effects. These inter-individual differences are observed not only among anticancer chemotherapeutics but in almost all drugs. Several studies have revealed that genetic factors are involved in these inter-individual differences. To date, the relationships have been revealed between adverse effects of some anticancer drugs and polymorphisms of drug metabolizing genes. Such relationships include 5-FU and DPYD gene, methotorexate and MTHFR gene, irinotecan and UGT 1A1 gene and 6-MP and TPMT gene. By using information on these polymorphisms, it will be possible to predict the occurrence of adverse effects before using anticancer drugs. In particular, information on polymorphisms related to the possibly adverse effects of irinotecan is now given in its package leaflet. This means that order-made medicine is a step closer. In this review, we discuss the relationships between polymorphisms of genes and the adverse effects of anticancer drugs. Furthermore, we want to suggest the direction of further pharmacogenomic studies with an eye to the realization of order-made medicine.
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PMID:[SNPs associated with adverse effects]. 1628 25

There is wide variability in the response of individuals to standard doses of drug therapy. This is an important problem in clinical practice, where it can lead to therapeutic failures or adverse drug reactions. Polymorphisms in genes coding for metabolising enzymes and drug transporters can affect drug efficacy and toxicity. Pharmacogenetics aims to identify individuals predisposed to a high risk of toxicity and low response from standard doses of anti-cancer drugs. This review focuses on the clinical significance of polymorphisms in drug-metabolising enzymes (cytochrome P450 [CYP] 2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4, CYP3A5, dihydropyrimidine dehydrogenase, uridine diphosphate glucuronosyltransferase [UGT] 1A1, glutathione S-transferase, sulfotransferase [SULT] 1A1, N-acetyltransferase [NAT], thiopurine methyltransferase [TPMT]) and drug transporters (P-glycoprotein [multidrug resistance 1], multidrug resistance protein 2 [MRP2], breast cancer resistance protein [BCRP]) in influencing efficacy and toxicity of chemotherapy. The most important example to demonstrate the influence of pharmacogenetics on anti-cancer therapy is TPMT. A decreased activity of TPMT, caused by genetic polymorphisms in the TPMT gene, causes severe toxicity with mercaptopurine. Dosage reduction is necessary for patients with heterozygous or homozygous mutation in this gene. Other polymorphisms showing the influence of pharmacogenetics in the chemotherapeutic treatment of cancer are discussed, such as UGT1A1*28. This polymorphism is associated with an increase in toxicity with irinotecan. Also, polymorphisms in the DPYD gene show a relation with fluorouracil-related toxicity; however, in most cases no clear association has been found for polymorphisms in drug-metabolising enzymes and drug transporters, and pharmacokinetics or pharmacodynamics of anti-cancer drugs. The studies discussed evaluate different regimens and tumour types and show that polymorphisms can have different, sometimes even contradictory, pharmacokinetic and pharmacodynamic effects in different tumours in response to different drugs. The clinical application of pharmacogenetics in cancer treatment will therefore require more detailed information of the different polymorphisms in drug-metabolising enzymes and drug transporters. Larger studies, in different ethnic populations, and extended with haplotype and linkage disequilibrium analysis, will be necessary for each anti-cancer drug separately.
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PMID:Genetic polymorphisms of drug-metabolising enzymes and drug transporters in the chemotherapeutic treatment of cancer. 1650 59

The pharmacogenetics of either individual patients or tumors has been used to aid the progress of personalized medicine to generate antitumor drugs (eg, trastuzamab and erlotinib) that are active against tumors expressing particular growth factor receptors. Outside the field of cancer therapeutics, pharmacogenetic tests have been introduced to detect patient genotypes with the aim of individualizing existing treatments. For example, the analysis of thiopurine S-methyltransferase genotypes enables the prediction of toxicity in patients to be treated with either 6-mercaptopurine or azathioprine, while the uridine 5'-diphosphoglucuronosyl-transferase 1A1 genotype may predict irinotecan toxicity. There is a large body of information concerning cytochrome P450 (CYP) polymorphisms and their relationship with drug toxicity and response; however, currently, there is limited use of CYP genotypes to individualize treatments. It is now well recognized that the CYP2C9 genotype, when combined with the genotype for vitamin K epoxide reductase complex subunit 1, is predictive of dose requirement for oral anticoagulants, a fact that is likely to have clinical utility. There is also potential to individualize treatments with certain drugs on the basis of CYP2D6, CYP2C19 and CYP3A5 genotypes. Studies on genes encoding drug receptors in relation to individualized prescription have been limited but there is increasing information on the relationship between response to beta2-adrenoceptor agonists and the genotype for the beta2-adrenoceptor gene. The introduction of pharmacogenetic tests into routine healthcare requires both a demonstration of cost-effectiveness and the availability of appropriate accessible testing systems.
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PMID:Individualized drug therapy. 1726 38

The Human Genome and the Hap Map Projects as well as the extensive use of deep resequencing worldwide, have contributed to a massive catalogue of reported single nucleotide polymorphisms (SNPs) and other genetic variations in the human genome. Pharmacogenomics is an emerging field that combines genetics with pharmacokinetics and pharmacodynamics of the drug in attempt to understand inter-individual differences among patients and develop more accurate drug dosing. However, only for the minority of those variations an association with phenotype has been established. Here, we provide an overview of genes and genetic variants that influence inter-individual dosing of three of the most widely used drugs, namely warfarin, irinotecan and thiopurine drugs, to highlight a tangible benefit of translating genomic knowledge into clinical practice. Therefore, particular SNPs in vitamin K epoxide reductase complex subunit 1 (VKORC1), cytochrome P450 2C9 (CYP2C9), uridine diphosphate glucoronosyltransferase 1A1 (UGT1A1) and thiopurine S-methyltransferase (TPMT) genes has proven to be applicable for optimising the dosage in pursuit of maximum efficacy and minimum adverse effects. Thus, they set an important paradigm of implementation of pharmacogenomics in the mainstream clinical practice.
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PMID:Clinical applicability of sequence variations in genes related to drug metabolism. 2145 74

Enzymes are critically important in the transportation, metabolism, and clearance of most therapeutic drugs used in clinical practice today. Many of these enzymes have significant genetic polymorphisms that affect the enzyme's rate kinetics. Regarding drug metabolism, specific polymorphisms to the cytochrome (CYP) P450 enzyme family are linked to phenotypes that describe reaction rates as "ultra", "intermediate", and "poor," as referenced to "extensive" metabolizers that are assigned to wildtype individuals. Activity scores is an alternate designation that provides more genotype-to-phenotype resolution. Understanding the relative change in enzyme activities or rate of clearance of specific drugs relative to an individual's genotypes is an important component in the interpretation of pharmacogenomic data for personalized medicine. Currently, the most relevant drug metabolizing enzymes are CYP 2D6, CYP 2C9, CYP 2C19, thiopurine methyltransferase (TPMT) and UDP-glucuronosyltransferase (UGT). Each of these enzymes is reactive to a host of different drug substrates. Pharmacogenomic tests that are in routine clinical practice include CYP 2C19 for clopidogrel, TPMT for thiopurine drugs, and UDP-1A1 for irinotecan. Other tests where there is considerable data but have not been widely implemented includes CYP 2C9 for warfarin, CYP 2D6 for tamoxifen and codeine, and CYP 2C19 for the proton pump inhibitors.
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PMID:Drug metabolizing enzyme activities versus genetic variances for drug of clinical pharmacogenomic relevance. 2190 84